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Tutorials > Kubernetes > Scaling Applications on Kubernetes

Scaling Applications on Kubernetes

Scaling applications up or down on Kubernetes is a key feature of the platform, and can be easily accomplished using the Kubernetes API or command-line tools. Here are some examples of how to scale your applications up or down on Kubernetes:

  • Scaling using the kubectl command-line tool:

To scale a deployment using the kubectl command-line tool, you can use the "kubectl scale" command. For example, to scale a deployment named "myapp-deployment" to five replicas, you would run the following command:

bash
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kubectl scale deployment/myapp-deployment --replicas=5

This command will update the deployment's desired replica count to five, and Kubernetes will automatically spin up new pods to reach the desired state.

  • Scaling using the Kubernetes API:

You can also scale a deployment programmatically using the Kubernetes API. Here is an example in Python:

python
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import kubernetes.client as k8sclient
from kubernetes.client.rest import ApiException

configuration = k8sclient.Configuration()
configuration.host = "http://localhost:8001"

api_instance = k8sclient.AppsV1Api(k8sclient.ApiClient(configuration))

deployment_name = "myapp-deployment"
namespace = "default"
scale_body = k8sclient.V1Scale(spec=k8sclient.V1ScaleSpec(replicas=5))

try:
    api_instance.patch_namespaced_deployment_scale(
        name=deployment_name,
        namespace=namespace,
        body=scale_body
    )
except ApiException as e:
    print("Exception when calling AppsV1Api: %s\n" % e)

This code will scale a deployment named "myapp-deployment" to five replicas in the "default" namespace. It uses the Kubernetes Python client library to interact with the Kubernetes API, and creates a V1Scale object to specify the desired replica count.

  • Horizontal Pod Autoscaling (HPA):

In addition to manual scaling, Kubernetes also supports automatic scaling using the Horizontal Pod Autoscaler (HPA). With HPA, Kubernetes will automatically adjust the replica count of a deployment based on CPU or memory utilization.

Here is an example HPA configuration:

yaml
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apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
metadata:
  name: myapp-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: myapp-deployment
  minReplicas: 1
  maxReplicas: 10
  metrics:
    - type: Resource
      resource:
        name: cpu
        targetAverageUtilization: 50

This YAML file defines an HPA named "myapp-hpa" that targets the "myapp-deployment" deployment. It will adjust the replica count between 1 and 10 based on CPU utilization, with a target utilization of 50%. If the CPU utilization goes above 50%, Kubernetes will automatically scale up the deployment to handle the increased load. If the utilization drops back down below 50%, Kubernetes will scale the deployment back down.



Next: Updating Applications on Kubernetes

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